1. Field of the Invention
The present invention relates to a technique of improving a power factor and, more particularly, to a power factor correction circuit capable of stably correcting an external input voltage although the external input voltage is unstably input.
2. Description of the Related Art
Recently, as the use of electrical energy has increased, due to the increasing use of electronic devices, stable supplies of power have been at issue. Nations around the world have tightened regulations regarding harmonic components generated from input terminals of electronic devices in order to minimize an influence of electronic devices on power lines and minimize interference in a different device.
In order to meet governmental regulations, various techniques have been provided for power factor correction circuits.
A power factor correction circuit may be classified as a passive power factor correction circuit including an inductor and a capacitor and an active power factor correction circuit using a switching converter. The passive power factor circuit has a large form factor and a low power factor, and is, consequently, limitedly used, while the active power factor correction circuit is widely used.
A power factor correction circuit employed in a related art power conversion module commonly uses a boundary conduction mode (BCM) based on zero voltage switching due to ease of implementation.
However, in the case of the BCM, when a low current is required for an input or when an input voltage is low, a switching frequency is increased to increase a switching loss, reducing efficiency.
In an effort to solve the problem, power factor correction circuits supporting various modes have been developed. For example, a power factor correction circuit using both a discontinuous conduction mode (DCM) and a continuous conduction mode (CCM), or the like, has been provided. Namely, when external input power is maintained, the CCM is used, and when an external input voltage is low, the DCM mode is used.
In this case, however, when an external input voltage is recovered, a returning operation is performed at a point at which a control level is high, increasing an output voltage to an over voltage protection (OVP) point at a stabilization time, so a protection mode is operational, and thus, a current is cut off.
Also, when a section in which a current is cut off is increased, an output current is unstable to cause a problem with a load control. In addition, a secondary problem such as noise generation, or the like, arises.
Related art documents below do not provide a solution to the foregoing problem.